German Chancellor Angela Merkel has expressed deep concern about repeated violations of a cease-fire between Ukrainian forces and Russia-backed separatists in eastern Ukraine.

Merkel's remarks on May 12 in Italy, where she was awarded a peace prize, came as the warring sides remain locked in a four-year conflict showing few signs that the violence might end soon.

Since April 2014, more than 10,300 people have been killed in fighting between Kyiv's forces and the separatists who control parts of the Donetsk and Luhansk regions.

Cease-fire deals announced as part of the Minsk accords -- September 2014 and February 2015 pacts aimed to resolve the conflict -- have failed to hold.

"Ukraine is worrying us," Merkel said after receiving the Lamp of Peace of St. Francis award in the Italian town of Assisi.

"We try to enforce the Minsk agreements, but every night there is a violation of the truce, every day human losses," she added.

A new cease-fire agreement between Ukraine and the Russia-backed separatists was reached in late 2017 and was meant to begin on December 23. But both sides have accused one another of repeated violations since then.